This document discusses organizing a Python meetup group in Groningen. It outlines topics for discussion including transitioning from Java to Python, readability differences between the languages, and the Python development cycle. Suggestions are made for logistics like meeting schedule, location, and topics of interest like web development, frameworks, and performance tuning. The document argues that Python has advantages over Java for readability and a more pragmatic, productive development cycle, though Java is safer and more widely adopted in large companies.

1. groningen.py / 16-01-2012

2. Schedule
• Input for Python meetups
• From Java to Python

3. Meetups
• groningen.py (thanks Mark)
• Talk and learn about Python development
• Community
• Regular meetings

4. What do we need?
• A time, space & some drinks
• Subjects / Format
• You!
• Please invite and suggest

5. How do you use python?
• For how long?
• Web
development?
• As main language?
• Framework?

6. Contents
• Any subject you’d like to hear about?
• Any subject you’d like to talk about?
python 3.0 web services
django 1.4 data migration
performance tuning

7. Meeting schedule
• How often?
• What day of week / time?

8. Let’s start
From Java to Python

9. Ivor Bosloper
using Geodjango
Preferred general purpose language:
Basic/
Assembler C Java Python
1985 1995 2001 2010

10. Java2py
Disclaimer: I love Java/JVM
• Typesafe/checked references
• Garbage collection
• Object Oriented
• Huge API
• General purpose
• Security, i18n
• Great debugging (e.g. with stacktraces)

11. Java2py
Why Python? Productivity!
• Readability
• Pragmatic and language possibilities
• Development cycle

12. Readability matters

13. Readability
public class HelloWorld {
public static void main(String[] args) {
System.out.println("Hello, World");
}
}

14. Readability
@Entity
public class Farm {
@Id @GeneratedValue
private Long id;
private String name;
@ManyToOne(optional=true)
private Address address;
public Long getId() {
return this.id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return this.name;
}
DRY
public void setName(String name) {
this.name = name;
}
public Address getAddress() {
return this.address;
}
public void setAddress(Address address) {
this.address = address;
}
public String toString() {
return this.name;
}
}

15. Readability

16. Readability
No .properties, .xml, sql (/hql)

17. Readability
XML Theory:
human readable
XML Practice:
Readability of a binary
combined with the
efficiency of flat text.

18. Flexibility
• XML or .properties configuration allows only
programmed logic
• settings.py allows custom logic

19. Readability

20. Pragmatic APIs
• APIs created for use, not for possibilities
DocumentBuilderFactory docBuilderFactory = DocumentBuilderFactory.newInstance();
DocumentBuilder docBuilder = docBuilderFactory.newDocumentBuilder();
Document doc = docBuilder.parse(new File("file.xml"));
XpathFactory xpf = XPathFactory.newInstance();
XPath xpath = xpf.newXPath();
NodeSet books = (NodeSet) xpath.evaluate("/Books/Book",doc,XpathConstants.NODESET);

21. Pragmatic APIs
• APIs created for use, not for possibilities
InputStream imageInputStream = FileInputStream("c.jpg");
SeekableStream seekableImageStream = SeekableStream.wrapInputStream(imageInputStream, true);
RenderedOp originalImage = JAI.create(JAI_STREAM_ACTION, seekableImageStream);
((OpImage) originalImage.getRendering()).setTileCache(null);
int origImageWidth = originalImage.getWidth();
double scale = 220.0 / originalImage.getWidth();
ParameterBlock paramBlock = new ParameterBlock();
paramBlock.addSource(originalImage); // The source image
paramBlock.add(scale); // The xScale
paramBlock.add(scale); // The yScale
paramBlock.add(0.0); // The x translation
paramBlock.add(0.0); // The y translation
RenderingHints qualityHints = new RenderingHints(RenderingHints.KEY_RENDERING,
RenderingHints.VALUE_RENDER_QUALITY);
RenderedOp resizedImage = JAI.create(JAI_SUBSAMPLE_AVERAGE_ACTION, paramBlock, qualityHints);
// lastly, write the newly-resized image to an output stream, in a specific encoding
FileOutputStream encoderOutputStream = new FileOutputStream("c-thumb.jpg");
JAI.create(JAI_ENCODE_ACTION, resizedImage, encoderOutputStream, JAI_ENCODE_FORMAT_JPEG, null);

22. Development cycle
• Getting started (Django)

23. Development cycle
Edit Save Edit Save
Reload page Reload page Compile
(2 seconds)
Restart Package
(war)
Deploy
(20 seconds)

24. Missing from py?
• Concurrency (!)
• Learn again: Performance tuning
• Safety of jvm
• (Adoption of big companies)

25. Concurrency?
• The free lunch
is over (2005)
• Azul 768-core
machine (2007)
• Python GIL in
2011?

26. Performance tuning
• Profiling
• GC options
• Memory

27. Safety of native code

28. Organizational adoption
• Commercial vendors
• Developer/deployer roles